JP6377268B2 - Honeycomb core, honeycomb sandwich structure, and honeycomb core manufacturing method - Google Patents

Description

  The present invention relates to a honeycomb core, a honeycomb sandwich structure including the honeycomb core, and a method for manufacturing the honeycomb core.

  In recent years, there has been an increasing demand for high resolution satellite images on outer space and the earth in various fields. Along with this, the development of observation satellites equipped with telescopes with higher resolution than before has been demanded. In such a satellite, in order to improve the resolution of the telescope, not only the size of the mirror is increased, but also sufficient rigidity to hold the large mirror when launched into outer space, and the thermal dimensions A telescope structure with stability is required.

  In the space environment, if the temperature distribution occurs in the telescope structure, if the thermal dimensional stability is low, the telescope structure will be distorted, leading to a decrease in the resolution of the satellite image. It becomes important.

  Here, as a prior example, a honeycomb sandwich structure composed of a carbon fiber reinforced plastic (CFRP) honeycomb core and a pair of CFRP skins covering both sides of the honeycomb core is proposed. (For example, refer to Patent Document 1).

  In the honeycomb sandwich structure described in Patent Document 1, the pair of skins are made of skin CFRP in which skin carbon fibers are arranged in a quasi-isotropic manner, and the honeycomb core has core carbon fibers arranged in a quasi-isotropic manner. Made of core CFRP. Conventionally, a honeycomb core has been manufactured with a core CFRP in which core carbon fibers are arranged obliquely with respect to the core height direction. However, in Patent Document 1, not only the core carbon fibers are arranged in the direction parallel to the skin surface, but also the core CFRP in which the core carbon fibers are arranged in the direction orthogonal to the skin surface. . With this configuration, a honeycomb sandwich structure having high rigidity and low thermal expansion can be obtained in the out-of-plane direction.

JP 2012-1013 A

However, the prior art has the following problems.
In the prior art described in Patent Document 1, using a CFRP honeycomb core and a CFRP skin, one of the two fiber directions of the carbon fiber constituting the core CFRP is parallel to the skin surface, The other is configured to be orthogonal to the skin surface. By doing so, in addition to the in-plane direction of the honeycomb sandwich structure, high rigidity and low thermal expansion in the out-of-plane direction can be realized.

  Here, in order to manufacture the above honeycomb sandwich structure, it is essential to use high elastic carbon fibers as carbon fibers for the core. However, when the high elastic carbon fiber prepreg is laid in a honeycomb core-shaped mold while the fiber direction of the high elastic carbon fiber prepreg obtained by impregnating the resin into the high elastic carbon fiber is parallel to the ribbon direction of the honeycomb core, Because of its high elastic modulus, it cannot be laid easily along the mold. As a result, a honeycomb core using high elastic carbon fibers cannot be easily formed.

  Further, it is possible to form a honeycomb core shape with a highly elastic carbon fiber prepreg using a dedicated jig or the like, and pressurize to form the honeycomb core. However, when the honeycomb core is formed by such a method, wrinkles or tension is locally generated with respect to the highly elastic carbon fiber prepreg, so that the characteristics such as mechanical characteristics or thermal characteristics of the honeycomb core are deteriorated.

  The present invention has been made to solve the above-described problems, and a honeycomb core that can be manufactured more easily than the conventional one regardless of the tensile elastic modulus of the carbon fiber prepreg as a material, and the honeycomb core It is an object of the present invention to obtain a honeycomb sandwich structure including the above and a method for manufacturing the honeycomb core.

The honeycomb core in the present invention is a honeycomb core configured to include carbon fibers having four or more different fiber directions, the ribbon direction of the honeycomb core being the X axis direction, and the cell width direction being orthogonal to the ribbon direction. When the direction perpendicular to the Y-axis direction, the ribbon direction, and the cell width direction is the Z-axis direction, each fiber direction on the honeycomb core surface parallel to the X-axis direction is defined by the X-axis direction and the Z-axis direction. The first fiber direction, the second fiber direction, the third fiber direction, and the fourth fiber direction are set in ascending order of the angle between each fiber direction and the X-axis direction, and the X-axis direction and the first fiber direction. The angle between the X-axis direction and the second fiber direction is 0 degree, the angle between the X-axis direction and the third fiber direction is 45 degrees, and the X-axis direction is -45 degrees. And the fourth fiber direction is 9 When the in which state the reference state whenever, as the fiber direction is not parallel to the X-axis direction and a state where the fiber direction is rotated from the reference state at a constant rotation angle, the honeycomb core, the An assembly in which the first carbon fiber bundles are knitted so that the first fiber direction and the third fiber direction are orthogonal to each other, and the second carbon fiber bundle is formed so that the second fiber direction and the fourth fiber direction are orthogonal to each other. And a knitted assembly .

  The honeycomb sandwich structure according to the present invention includes a honeycomb core and a pair of skins that are bonded to the honeycomb core and sandwich the honeycomb core.

  The honeycomb core manufacturing method according to the present invention includes a prepreg sheet obtained by impregnating carbon fiber with a resin and a plurality of semi-hexagonal columnar protrusions formed in parallel with each other, the first jig and the first jig A method for manufacturing a honeycomb core including carbon fibers having four or more different fiber directions by using the jig 2 and a plurality of hexagonal cores, The X direction is the X axis direction, the cell width direction orthogonal to the ribbon direction is the Y axis direction, and the ribbon direction and the direction orthogonal to the cell width direction are the Z axis direction, The first fiber direction, the second fiber direction, the third fiber direction, and the fourth fiber in ascending order of the angle formed with the X-axis direction among the fiber directions. Direction, X-axis direction and first fiber The angle formed by the direction is −45 degrees, the angle formed by the X axis direction and the second fiber direction is 0 degrees, the angle formed by the X axis direction and the third fiber direction is 45 degrees, and the X axis When a state in which the angle formed between the direction and the fourth fiber direction is 90 degrees is set as a reference state, the carbon fibers contained in the prepreg sheet are disposed while interposing a plurality of cores one by one in parallel with the Z-axis direction. In order to prevent the fiber direction from being parallel to the X-axis direction, a plurality of layers of prepreg sheets are sequentially stacked on the first jig so that each fiber direction is rotated from the reference state at a constant rotation angle. The two jigs are further overlapped and heated under pressure, and then a plurality of cores are extracted to produce a honeycomb core.

  According to the present invention, a honeycomb core that can be manufactured more easily than before regardless of the tensile modulus of the carbon fiber prepreg as a material, a honeycomb sandwich structure including the honeycomb core, and manufacture of the honeycomb core You can get the method.

It is a disassembled perspective view which shows the structure of the honeycomb sandwich structure in Embodiment 1 of this invention. FIG. 2 is a perspective view showing a state in which a honeycomb core prepreg sheet that is a material of the honeycomb core of FIG. 1 is laid on a first jig. The state when the second jig is stacked on the laminate formed by further stacking the honeycomb core prepreg sheet on the first jig through the plurality of cores from the state of FIG. It is front sectional drawing when seeing from the Z-axis direction. It is explanatory drawing which shows the installation method different from the installation method to the 1st jig | tool of the prepreg sheet | seat for honeycomb cores in Embodiment 1 of this invention as a comparative example. It is explanatory drawing which shows the laying method to the 1st jig | tool of the prepreg sheet for honeycomb cores in Embodiment 1 of this invention. FIG. 4 is a graph showing the relationship between the rotation angle θ when only the second layer prepreg sheet for honeycomb core is rotated by the rotation angle θ, and the out-of-plane direction characteristics of the honeycomb sandwich structure. It is. Relationship between the rotation angle θ when the honeycomb core prepreg sheet is rotated by the rotation angle θ and the out-of-plane direction characteristics of the honeycomb sandwich structure with respect to FIG. It is a graph which shows. It is a graph which shows the relationship between the tensile elasticity modulus of a carbon fiber used for producing the honeycomb core in Embodiment 1 of this invention, and a thermal expansion coefficient. [Fig. 3] Fig. 3 is a cross-sectional view showing a configuration of a measurement system for measuring an out-of-plane thermal expansion coefficient of the honeycomb sandwich structure according to Embodiment 1 of the present invention. 4 is a graph showing a relationship between a cell width size and a rotation angle θ when a honeycomb core in Embodiment 1 of the present invention can be formed.

  Hereinafter, a honeycomb core, a honeycomb sandwich structure, and a method for manufacturing a honeycomb core according to the present invention will be described according to preferred embodiments with reference to the drawings. In the description of the drawings, the same portions or corresponding portions are denoted by the same reference numerals, and redundant description is omitted. In addition, examples of the use of the honeycomb core and the honeycomb sandwich structure according to the present invention include aerospace applications.

Embodiment 1 FIG.
A honeycomb sandwich structure 1 according to the first embodiment includes a honeycomb core 3 and a pair of skins 2 that are bonded to the honeycomb core 3 and sandwich the honeycomb core 3 therebetween. Specifically, the honeycomb sandwich structure 1 is configured as shown in FIG. FIG. 1 is an exploded perspective view showing a configuration of a honeycomb sandwich structure 1 according to Embodiment 1 of the present invention.

  In the honeycomb sandwich structure 1 in FIG. 1, a pair of skins 2 made of CFRP is disposed so as to cover both end surfaces in the height direction of a honeycomb core 3 made of CFRP through a sheet adhesive 4. Has been. Further, the pair of skins 2 arranged in this way are fixed to the honeycomb core 3.

  More specifically, the thermosetting sheet adhesive 4 is laid on the surface of the pair of skins 2, and is installed on the honeycomb core 3 on one surface of the pair of skins 2 on which the sheet adhesive 4 is laid. To do. Subsequently, the honeycomb sandwich structure is formed by covering the honeycomb core 3 with the other of the pair of skins 2 on which the sheet-like adhesive 4 is laid, and heating the sheet-like adhesive 4 by heating under pressure. 1 is produced.

  Here, among the in-plane directions of the honeycomb sandwich structure 1, the ribbon direction of the honeycomb core 3 is defined as the X-axis direction, and the cell width direction of the honeycomb core 3 is defined as the Y-axis direction. The out-of-plane direction of the honeycomb sandwich structure 1 is the Z-axis direction. Note that the X-axis direction and the Y-axis direction are orthogonal to each other, and the Z-axis direction is orthogonal to the X-axis direction and the Y-axis direction.

  In order to indicate the fiber directions of the carbon fibers contained in each of the skin 2 and the honeycomb core 3, in the skin 2, the 0-degree direction is the X-axis direction, the 90-degree direction is the Y-axis direction, and the honeycomb core 3 is The 0 degree direction is the Z axis direction, and the 90 degree direction is the X axis direction.

  Next, an example of a method for manufacturing the skin 2 of the honeycomb sandwich structure 1 will be described. First, for example, a cyanate resin EX1515 (manufactured by TENCATE) is impregnated into an assembly produced by weaving a bundle of high-elasticity carbon fibers M60J (manufactured by Toray) whose length directions are aligned so as to be orthogonal to each other. A biaxially oriented prepreg sheet for the skin is prepared. At this time, the highly elastic carbon fiber M60J is a bundle of long fibers (filaments) having a diameter of 5 μm to 7 μm.

  Subsequently, the laminated body of the prepreg sheets for skin formed by sequentially stacking a plurality of the prepreg sheets for skin prepared as described above is heated at a temperature of about 120 to 180 ° C. under a pressure of about 3 atm. To cure. Thus, the skin 2 is produced by hardening the laminated body of the prepreg sheet for skin.

  Here, as a method of sequentially stacking the prepreg sheets for the skin, for example, the prepreg sheets for the skin are set to 0 degrees with respect to the direction in which the first sheet is placed, and 0 degrees, 60 degrees, -60 degrees, -60 Stack 6 sheets in the order of degrees, 60 degrees, and 0 degrees. The prepreg sheets for the skin may be stacked in the order of 0 degree, 45 degrees, -45 degrees, 90 degrees, 90 degrees, -45 degrees, 45 degrees, and 0 degrees. The skin 2 made of CFRP produced by curing the laminate formed by stacking the prepreg sheets for the skin in this way has pseudo-isotropic properties that make the properties almost equal in all directions parallel to the skin surface. Have.

  Note that when the cyanate resin EX1515 impregnated in the aggregate of the high elastic carbon fibers M60J constituting the skin 2 functions as an adhesive, the honeycomb core 3 of one of the pair of skins 2 is used without using the sheet-like adhesive 4. Alternatively, the honeycomb sandwich structure 1 may be manufactured by stacking the other of the pair of skins 2 in the order of the other and heating under pressure.

  Next, an example of a method for manufacturing the honeycomb core 3 of the honeycomb sandwich structure 1 will be described with reference to FIGS. 2 and 3. FIG. 2 is a perspective view showing a state in which the honeycomb core prepreg sheet 5 which is the material of the honeycomb core 3 of FIG. 1 is laid on the first jig 6. FIG. 3 shows a state in which a second cured product is formed from the state shown in FIG. 2 by stacking the honeycomb core prepreg sheet 5 on the first jig 6 with a plurality of cores 8 interposed therebetween. It is front sectional drawing when the state when the tool 9 is piled up is seen from the Z-axis direction.

  FIG. 2 also shows a jig coordinate system in which the short direction of the protrusion 7 formed on the first jig 6 is the X-axis direction and the long direction of the protrusion 7 is the Z-axis direction. Yes. The X-axis direction and the Z-axis direction in the jig coordinate system coincide with the X-axis direction and the Z-axis direction in FIG.

  First, for example, cyanate resin NM-31 (manufactured by JX Nippon Mining & Energy Co., Ltd.) is assembled into an assembly produced by weaving a bundle of high-elasticity carbon fibers YS80A (manufactured by Nippon Graphite Fiber) having the same length direction. ) Is impregnated to produce a biaxially oriented honeycomb core prepreg sheet 5 (hereinafter simply referred to as prepreg sheet 5). At this time, the highly elastic carbon fiber YS80A is a bundle of long fibers (filaments) having a diameter of 7 μm to 10 μm.

  Subsequently, the prepreg sheet 5 is formed into the shape of the honeycomb core 3 using the first jig 6, the plurality of cores 8, and the second jig 9. The first jig 6 is a surface plate having a plurality of semi-hexagonal columnar protrusions 7 formed in parallel with each other. Each of the plurality of cores 8 has a hexagonal column shape. Similar to the first jig 6, the second jig 9 has a plurality of semi-hexagonal columnar protrusions 10 formed in parallel with each other.

  Specifically, as shown in FIG. 2, at least two prepreg sheets 5 are laid in accordance with the shape of the first jig 6, and then a plurality of cores 8 are arranged one by one on the adjacent protrusions 7. Overlap at the position of the groove between. Subsequently, at least two layers of the prepreg sheet 5 are laid in accordance with the shape of the first jig 6 on which the plurality of cores 8 are stacked, and then the plurality of cores 8 are placed one by one at the position of the protrusion 7. Overlay on. Thus, after repeating the process of overlapping the prepreg sheet 5 and the plurality of cores 8 a plurality of times, the plurality of cores 8 are stacked on the second jig 9 paired with the first jig 6. If the first jig 6 is overlapped in accordance with the shape of the first jig 6, the state shown in FIG. 3 is obtained.

  Subsequently, in the state illustrated in FIG. 3, the laminated body is cured by heating under pressure, and then the plurality of cores 8 are extracted, whereby the honeycomb core 3 is manufactured.

  Here, as a method for laying the prepreg sheet 5 on the first jig 6, the prepreg sheet 5 has a direction of each fiber so that the fiber direction of the carbon fibers contained in the prepreg sheet 5 is not parallel to the X-axis direction. The first jig 6 is laid so as to be in a state of being rotated at a certain rotation angle θ described later from a reference state described later. For example, a prepreg sheet 5 having a fiber direction of θ degrees and (90 + θ) degrees is prepared by cutting in advance a prepreg sheet having a fiber direction of 0 degrees and 90 degrees. Similarly, a prepreg sheet 5 having a fiber direction of (−45 + θ) degree and (45 + θ) degree is prepared by cutting in advance a prepreg sheet having a fiber direction of −45 degrees and 45 degrees. Subsequently, when these prepreg sheets 5 are laid on the first jig 6, they are laminated in accordance with the sheet shape.

  In other words, each fiber direction is a reference so that the fiber directions of the carbon fibers contained in the prepreg sheet 5 are not parallel to the X-axis direction while interposing a plurality of cores 8 one by one in parallel with the Z-axis direction. The prepreg sheet 5 is sequentially stacked on the first jig 6 for a plurality of layers so as to be rotated at a constant rotation angle θ from the state, and the second jig 9 is further stacked. Subsequently, after heating under pressure, a plurality of cores 8 are extracted, whereby a honeycomb core 3 including carbon fibers having four different fiber directions is manufactured.

  Hereinafter, effects obtained by such a laying method will be described with reference to FIGS. 4 and 5. FIG. 4 is an explanatory diagram showing a laying method different from the laying method of the prepreg sheet 5 on the first jig 6 in Embodiment 1 of the present invention as a comparative example. FIG. 5 is an explanatory diagram showing a method of laying the prepreg sheet 5 on the first jig 6 in Embodiment 1 of the present invention.

  4 and 5 also illustrate a material coordinate system in which the 0-degree direction is the Z-axis direction and the 90-degree direction is the X-axis direction in the fiber direction of the carbon fiber. The X-axis direction and the Z-axis direction in the material coordinate system coincide with the X-axis direction and the Z-axis direction in FIG.

  The comparative example of FIG. 4 corresponds to the prior art described in Patent Document 1, and one of the four different fiber directions arranged in a 45-degree pitch parallel to the XZ plane is parallel to the X axis. The honeycomb core 3 is configured to include carbon fibers. With this configuration, the carbon fibers of the honeycomb core 3 are arranged in a pseudo isotropic manner.

  In order to produce the honeycomb core 3 having such a configuration, the first direction is such that the angle formed by the fiber direction of the carbon fiber contained in the prepreg sheet 5 and the X-axis direction is 45 degrees and −45 degrees. It is necessary to lay the first prepreg sheet 5 on the jig 6. Furthermore, it is necessary to lay the second-layer prepreg sheet 5 on the first-layer prepreg sheet 5 so that the angles formed by the fiber direction of the carbon fiber and the X-axis direction are 0 degrees and 90 degrees.

  Here, when attention was paid to the prepreg sheets 5 of the first layer and the second layer, the following knowledge could be obtained. That is, the first prepreg sheet 5 has good stretchability in the X-axis direction (indicated by a white arrow in the figure), and therefore the first jig 6 along the mold of the first jig 6. The second prepreg sheet 5 is difficult to expand and contract in the X-axis direction, but it is difficult to follow the mold of the first jig 6. In this case, the honeycomb core 3 cannot be easily formed. Moreover, when a large load was applied using a dedicated jig and the second-layer prepreg sheet 5 was laid on the first jig 6, the carbon fibers in the second-layer prepreg sheet 5 were broken. Oops. In this case, although the honeycomb core 3 can be formed, characteristics such as mechanical characteristics or thermal characteristics are deteriorated.

  On the other hand, in the present invention, each of the four fiber directions on the honeycomb core surface parallel to the X-axis direction is parallel to the XZ plane and includes carbon fibers having different directions from the X-axis direction. A core 3 is configured. By configuring the honeycomb core 3 in this way, the angle formed by the fiber direction of the carbon fibers contained in the prepreg sheet 5 and the X-axis direction does not become 0 degrees, so the prepreg sheet 5 is attached to the first jig 6. When laying, it can be made to follow the mold of the first jig 6. Therefore, the honeycomb core 3 can be easily formed. In addition, unlike the above, the carbon fibers in the first and second prepreg sheets 5 do not break, and characteristics such as mechanical characteristics or thermal characteristics are not deteriorated.

  As described above, in the honeycomb core 3 including carbon fibers having four different fiber directions, the fiber directions on the honeycomb core surface parallel to the X-axis direction are not parallel to the X-axis direction. Each fiber direction is configured to be rotated from the reference state by a constant rotation angle θ. Thus, when the prepreg sheet 5 is laid on the first jig 6, the prepreg sheet 5 can be placed along the mold of the first jig 6, and the honeycomb core 3 can be easily formed.

  4 and 5, the first fiber direction, the second fiber direction, the third fiber direction, the fourth fiber direction of the carbon fibers included in the honeycomb core 3 in ascending order of the angle with the X-axis direction. When the fiber direction is set, the angle formed by the first fiber direction and the third fiber direction and the angle formed by the second fiber direction and the fourth fiber direction are both 90 degrees. doing. Further, as shown in FIG. 4, the angle formed by the X-axis direction and the first fiber direction is −45 degrees, the angle formed by the X-axis direction and the second fiber direction is 0 degrees, and the X-axis direction A state where the angle formed by the third fiber direction is 45 degrees and the angle formed by the X-axis direction and the fourth fiber direction is 90 degrees is referred to as a reference state.

  4 and 5, an assembly produced by weaving the first carbon fiber bundle so that the first fiber direction and the third fiber direction are orthogonal to each other, and the second fiber direction and the fourth fiber direction. The case where the honeycomb core 3 is configured including the aggregate produced by weaving the second carbon fiber bundle so that the two are orthogonal to each other is illustrated.

  Here, in particular, as shown in FIG. 5, the first and second prepreg sheets 5 are rotated so that the fiber direction of the carbon fiber shown in FIG. 4 is rotated by the rotation angle θ with respect to the X-axis direction. Lay it on the first jig 6. That is, the angle formed between the fiber direction of the carbon fiber contained in the first prepreg sheet 5 and the X-axis direction is (45 + θ) degrees and (−45 + θ) degrees, and the carbon contained in the second prepreg sheet 5. The angles formed by the fiber direction of the fiber and the X-axis direction are set to θ degrees and (90 + θ) degrees. That is, each fiber direction is rotated from the reference state at a constant rotation angle θ so that each fiber direction is not parallel to the X-axis direction.

  In this case, not only the different fiber directions of the carbon fibers are not parallel to the X-axis direction, but also the fiber directions of the first-layer carbon fibers are orthogonal to each other and the fiber directions of the second-layer carbon fibers are also mutually Orthogonal. By devising in this way, when the prepreg sheet 5 is laid on the first jig 6, it can be made to follow the mold of the first jig 6, and the honeycomb core 3 can be easily formed. Furthermore, a honeycomb core 3 in which carbon fibers are arranged in a pseudo isotropic manner can be produced.

  As a result of intensive studies, it was found that the range of the rotation angle θ that can be laid on the first jig 6 of the prepreg sheet 5 varies depending on the cell width size of the honeycomb core 3. As a specific example, when the carbon fiber contained in the prepreg sheet 5 is a high elastic carbon fiber having a tensile modulus of 500 GPa or more, when the cell width size of the honeycomb core 3 is 9.5 mm, the rotation angle θ is 12 degrees or more. When the honeycomb core 3 has a cell width size of 6.4 mm, it was confirmed that the rotation angle θ is in the range of 17 degrees to 28 degrees. Moreover, when the cell width size of the honeycomb core 3 was 4.8 mm, it was confirmed that the rotation angle θ was in the range of 20 degrees to 25 degrees. FIG. 10 is a graph showing the relationship between the cell width size and the rotation angle θ when the honeycomb core 3 in the first embodiment of the present invention can be formed. In FIG. 10, the above results, that is, the cell width size and the rotation angle θ when the honeycomb core 3 can be formed are plotted, thereby illustrating the region where the CFRP honeycomb core 3 can be formed. In the figure, this region is indicated as a CFRP honeycomb core moldable region.

  Next, the relationship between the rotation angle θ when the honeycomb core 3 is produced and the out-of-plane direction characteristics of the honeycomb sandwich structure 1 including the honeycomb core 3 will be described with reference to FIGS. 6 and 7.

  6 shows the rotation angle θ when the honeycomb core 3 is manufactured by rotating only the second-layer prepreg sheet 5 with respect to FIG. 4 by the rotation angle θ, and the out-of-plane characteristics of the honeycomb sandwich structure 1. It is a graph which shows a relationship. 7 shows the rotation angle θ when the honeycomb core 3 is manufactured by rotating both the first and second prepreg sheets 5 with respect to FIG. 4 by the rotation angle θ, and the out-of-plane direction of the honeycomb sandwich structure 1. It is a graph which shows the relationship with a characteristic. 6 and 7 show changes in the tensile modulus and the thermal expansion coefficient as changes in the out-of-plane characteristics of the honeycomb sandwich structure 1.

  Here, only the second-layer prepreg sheet 5 that is difficult to be laid on the first jig 6, that is, the prepreg sheet 5 having an angle between the fiber direction of the carbon fiber and the X-axis direction of 0 degrees and 90 degrees. Consider a case where the honeycomb core 3 is manufactured by rotating it by the rotation angle θ. In this case, when the prepreg sheet 5 is laid on the first jig 6, it can be placed along the mold of the first jig 6, and the honeycomb core 3 can be easily formed. However, as shown in FIG. 6, the tensile elastic modulus in the out-of-plane direction of the honeycomb sandwich structure 1 is lowered depending on the magnitude of the rotation angle θ.

  Therefore, in order to suppress a decrease in the tensile elastic modulus in the out-of-plane direction of the honeycomb sandwich structure 1, the first and second prepreg sheets 5 are rotated by the rotation angle θ to produce the honeycomb core 3. Also in this case, when the prepreg sheet 5 is laid on the first jig 6, it can follow the mold of the first jig 6, and the honeycomb core 3 can be easily formed. Furthermore, since the honeycomb core 3 in which carbon fibers are arranged in a pseudo isotropic manner is produced, as shown in FIG. 7, the tensile elastic modulus in the out-of-plane direction of the honeycomb sandwich structure 1 depends on the rotation angle θ. It remains constant without degrading.

  Thus, each fiber direction is rotated from the reference state at a constant rotation angle θ so that the fiber directions of the carbon fibers on the honeycomb core surface parallel to the X-axis direction are not parallel to the X-axis direction. The honeycomb core 3 is configured as described above. Thereby, the honeycomb core 3 can be easily formed, and the honeycomb core 3 in which the carbon fibers are arranged in a pseudo isotropic manner can be manufactured.

  Next, the carbon fibers contained in the honeycomb core 3 will be described with reference to FIG. FIG. 8 is a graph showing the relationship between the tensile elastic modulus and the thermal expansion coefficient of the carbon fiber used to produce the honeycomb core 3 in the first embodiment of the present invention. As shown in FIG. 8, the carbon fiber has a characteristic that the thermal expansion coefficient increases in the negative direction as the tensile elastic modulus increases.

  Here, the out-of-plane thermal expansion coefficient of the honeycomb sandwich structure 1 is the product of the out-of-plane thermal expansion coefficient and the plate thickness of the two skins 2 and the out-of-plane heat of the two sheet-like adhesives 4. This is a value obtained by dividing the sum of the product of the expansion coefficient and the plate thickness and the product of the out-of-plane thermal expansion coefficient and the height of the honeycomb core 3 by the height of the honeycomb sandwich structure 1.

  At this time, the in-plane thermal expansion coefficient of the skin 2 is offset by the carbon fiber having the negative thermal expansion coefficient and the resin having the positive thermal expansion coefficient as described above, and becomes a value close to zero. On the other hand, the thermal expansion coefficient in the out-of-plane direction of the skin 2 becomes a positive thermal expansion coefficient because the thermal expansion of the resin is dominant because the carbon fibers are not continuously arranged. Further, the in-plane and out-of-plane thermal expansion coefficients of the sheet adhesive 4 are also positive thermal expansion coefficients.

  Therefore, the out-of-plane thermal expansion coefficients of the two skins 2 and the sheet-like adhesive 4 are positive values in a range of about 20 ppm / ° C. to 70 ppm / ° C., for example. Therefore, in order to make the out-of-plane thermal expansion coefficient of the honeycomb sandwich structure 1 close to zero, the out-of-plane thermal expansion coefficient of the honeycomb core 3 needs to be as negative as possible.

  Therefore, in the present invention, the honeycomb core 3 is manufactured using high elastic carbon fibers, that is, carbon fibers having a large negative thermal expansion coefficient, and the honeycomb sandwich structure 1 is manufactured including the honeycomb core 3. Thereby, the honeycomb sandwich structure 1 having high rigidity and low thermal expansion in the out-of-plane direction can be realized.

  The in-plane thermal expansion coefficient of the honeycomb sandwich structure 1 is the relationship between the tensile modulus and the in-plane thermal expansion coefficient of the two skins 2, the two sheet-like adhesives 4, and the honeycomb core 3. The honeycomb sandwich structure 1 having high rigidity and low thermal expansion in the in-plane direction and the out-of-plane direction can be realized by adjusting the coefficient of thermal expansion in the out-of-plane direction.

  Next, an example of the result of measuring the out-of-plane thermal expansion coefficient of the honeycomb sandwich structure 1 will be described with reference to FIG. FIG. 9 is a cross-sectional view showing a configuration of a measurement system for measuring the out-of-plane thermal expansion coefficient of honeycomb sandwich structure 1 in Embodiment 1 of the present invention.

  As shown in FIG. 9, the honeycomb sandwich structure 1 is mounted on the sample support 11 with the laser reflecting mirror 13 bonded and fixed to the pair of skins 2 and placed in the thermostatic chamber 12. By controlling the temperature in the thermostatic chamber 12, the temperature of the honeycomb sandwich structure 1 can be changed. Further, the thermal expansion coefficient is calculated by irradiating the laser beam from the laser focus displacement meter 14, receiving the reflected light from the laser reflecting mirror 13, and measuring the displacement amount of the honeycomb sandwich structure 1 by heating.

  In the honeycomb sandwich structure 1 that is a measurement target of the measurement system shown in FIG. 9, the thickness of the skin 2 is 0.72 mm, and the thickness of the sheet adhesive 4 is 0.06 mm.

  Further, the honeycomb core 3 of the honeycomb sandwich structure 1 to be measured is manufactured by rotating the first and second prepreg sheets 5 by 22.5 degrees as the rotation angle θ in the material coordinate system shown in FIG. Has been. That is, the angle formed between the fiber direction of the carbon fibers contained in the first-layer prepreg sheet 5 and the X-axis direction is (45 + 22.5) degrees and (−45 + 22.5) degrees, and the second-layer prepreg sheet 5 Each prepreg sheet 5 is laid on the first jig 6 so that the angle formed by the fiber direction of the carbon fibers contained in the X-axis direction is (0 + 22.5) degrees and (90 + 22.5) degrees. Thus, the honeycomb core 3 is produced. Further, the honeycomb core has a cell size of 1/4 inch and a height of 122.0 mm.

  The result of measuring the out-of-plane expansion coefficient of such a honeycomb sandwich structure 1 by the measurement system shown in FIG. 9 was 0.08 ppm / ° C.

  Further, in the honeycomb sandwich structure 1, even when the cell size of the honeycomb core 3 is changed from 1/4 inch to 3/8 inch, the out-of-plane thermal expansion coefficient is 0.08 ppm / ° C. there were. Normally, the cell size of the honeycomb core 3 is often set to 1/4 inch or 3/8 inch, but almost the same thermal expansion coefficient can be expected as an intermediate size.

  As described above, even if the honeycomb core 3 of the honeycomb sandwich structure 1 is formed using a prepreg sheet containing high elastic carbon fibers, local wrinkles and tension are not generated. Therefore, it is possible to increase the rigidity of the honeycomb sandwich structure 1 and to make the thermal expansion coefficient substantially zero. Therefore, the honeycomb sandwich structure 1 having high rigidity and low thermal expansion in the out-of-plane direction can be realized by the configuration of the honeycomb core 3 in the present invention.

  In the first embodiment, the case where the high elastic carbon fiber YS80A having a tensile elastic modulus of about 785 GPa is used as the carbon fiber contained in the honeycomb core 3 is not limited to this. The present invention can be applied regardless of the tensile modulus of the carbon fiber contained.

  In particular, as shown in FIG. 8, the coefficient of thermal expansion of a highly elastic carbon fiber having a tensile elastic modulus of 500 GPa or more is substantially constant. Therefore, if the honeycomb core 3 made of a high elastic carbon fiber having a tensile elastic modulus of 500 GPa or more is used, the out-of-plane thermal expansion coefficient of the honeycomb sandwich structure 1 can be made substantially zero. Therefore, it is preferable to use carbon fibers having a tensile modulus of 500 GPa or more as the carbon fibers contained in the honeycomb core 3.

  In the first embodiment, the honeycomb core 3 is exemplified to include carbon fibers having four different fiber directions. However, the present invention is not limited to this, and the four or more different fibers are different from each other. You may comprise including the carbon fiber which has a direction. For example, in FIG. 5, if the prepreg sheet 5 is further laid as the third layer so as not to coincide with the fiber directions of the carbon fibers contained in the first and second prepreg sheets 5, the honeycomb core 3 is included. It is possible for the carbon fibers to have six different fiber directions. In this way, even when the carbon fibers included in the honeycomb core 3 are configured to have four or more different fiber directions, the four or more directions on the honeycomb core surface parallel to the X-axis direction can be used. Each fiber direction of the fiber direction is parallel to the XZ plane, and further, each fiber direction is rotated from the reference state by a constant rotation angle θ so that each fiber direction is not parallel to the X-axis direction. Configure.

  In the first embodiment, the case where the biaxially oriented prepreg sheet 5 including an assembly produced by braiding carbon fiber bundles so as to be orthogonal to each other is illustrated, but the present invention is not limited to this. That is, as long as it is a biaxially oriented prepreg sheet, not only the prepreg sheet 5 including an assembly produced by braiding carbon fiber bundles so as to be orthogonal to each other, any prepreg sheet may be used. In the biaxially oriented prepreg sheet, the fiber directions do not have to be orthogonal to each other.

  In the first embodiment, the case where the honeycomb core 3 is configured to include carbon fibers having four different fiber directions using the biaxially oriented prepreg sheet 5 is illustrated, but the present invention is not limited thereto. Not. That is, the honeycomb core 3 may be configured using carbon fibers having four different fiber directions by using a uniaxial prepreg sheet. In this case, unlike FIG. 5, four layers of uniaxial prepreg sheets are used so that the carbon fibers contained in the honeycomb core 3 have four different fiber directions.

  In the first embodiment, the case where each of the pair of skins 2 is configured by stacking the prepreg sheets for the skin so that the fiber directions of the carbon fibers are symmetric with respect to the Z-axis direction is illustrated. The skin 2 may be configured by laminating prepreg sheets for skin so that the fiber direction of the carbon fibers is symmetrical with respect to the Z-axis direction about the honeycomb core 3.

  As described above, according to the first embodiment, in the honeycomb core configured to include carbon fibers having four or more different fiber directions, the angles formed by the X-axis direction and the fiber direction of the carbon fibers are each −45. When a state of degrees, 0 degrees, 45 degrees, and 90 degrees is set as a reference state, each fiber direction is rotated from the reference state at a constant rotation angle so that each fiber direction is not parallel to the X-axis direction; Configure to be

  A honeycomb core having such a configuration can be manufactured more easily than the conventional one regardless of the tensile modulus of the carbon fiber prepreg as a material. In addition, even if the prepreg sheet is laid on the first jig, that is, the honeycomb core-shaped mold, it is easy to lay the prepreg sheet on the mold without generating wrinkles or tension. Enables easy molding.

Claims (5)

A honeycomb core comprising carbon fibers having four or more different fiber directions,
When the ribbon direction of the honeycomb core is the X-axis direction, the cell width direction orthogonal to the ribbon direction is the Y-axis direction, and the ribbon direction and the direction orthogonal to the cell width direction are the Z-axis direction,
Each fiber direction in the honeycomb core surface parallel to the X-axis direction is parallel to an XZ plane constituted by the X-axis direction and the Z-axis direction,
Among the fiber directions, the first fiber direction, the second fiber direction, the third fiber direction, and the fourth fiber direction in ascending order of the angle with the X-axis direction,
The angle formed by the X-axis direction and the first fiber direction is −45 degrees, the angle formed by the X-axis direction and the second fiber direction is 0 degrees, and the X-axis direction and the third fiber When the angle formed by the direction is 45 degrees and the state where the angle formed by the X-axis direction and the fourth fiber direction is 90 degrees is set as a reference state,
Each fiber direction is rotated from the reference state at a certain rotation angle so that each fiber direction is not parallel to the X-axis direction ,
The honeycomb core is
An assembly in which the first carbon fiber bundle is knitted so that the first fiber direction and the third fiber direction are orthogonal to each other;
An assembly in which a second carbon fiber bundle is knitted so that the second fiber direction and the fourth fiber direction are orthogonal to each other;
Honeycomb core composed of containing . The honeycomb core according to claim 1, wherein the rotation angle is included in a range of 12 degrees to 33 degrees. The honeycomb core according to claim 1 or 2 , wherein the carbon fiber has a tensile modulus of 500 GPa or more. The honeycomb core according to any one of claims 1 to 3 ,
A pair of skins sandwiching the honeycomb core by being bonded to the honeycomb core;
Honeycomb sandwich structure with A prepreg sheet obtained by impregnating carbon fiber with a resin;
A first jig and a second jig having a plurality of semi-hexagonal columnar protrusions formed in parallel with each other;
A plurality of hexagonal cores,
A method for manufacturing a honeycomb core including the carbon fibers having fiber directions of four or more directions different from each other,
When the ribbon direction of the honeycomb core is the X-axis direction, the cell width direction orthogonal to the ribbon direction is the Y-axis direction, and the ribbon direction and the direction orthogonal to the cell width direction are the Z-axis direction,
The short direction of the plurality of protrusions is the X-axis direction, and the long direction of the plurality of protrusions is the Z-axis direction,
Among the fiber directions, the first fiber direction, the second fiber direction, the third fiber direction, and the fourth fiber direction in ascending order of the angle with the X-axis direction,
The angle formed by the X-axis direction and the first fiber direction is −45 degrees, the angle formed by the X-axis direction and the second fiber direction is 0 degrees, and the X-axis direction and the third fiber When the angle formed by the direction is 45 degrees and the state where the angle formed by the X-axis direction and the fourth fiber direction is 90 degrees is set as a reference state,
While interposing the plurality of cores one by one in parallel with the Z-axis direction, the fiber directions of the carbon fibers included in the prepreg sheet are not parallel to the X-axis direction. The prepreg sheet was sequentially stacked on the first jig for a plurality of layers so as to be rotated at a certain rotation angle from the reference state, and the second jig was further stacked and heated under pressure. Thereafter, the honeycomb core is manufactured by extracting the plurality of cores. A method for manufacturing a honeycomb core.

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